A breeding colony of healthy uniform marmosets of the genera Callithrix and Saguinus is being developed in an indoor-outdoor environment for utilization in biomedical research and teaching at Texas A&M University and other institutions. Aerobic and anaerobic fecal and oral microflora are monitored and improved methods are being developed to detect significant pathogens (e.g., enteropathogenic Escherichia coli, Shigella sp, Clostridium sp) and R-factor bearing organisms. Electrophoretic and immunoelectrophoretic profiles of human and marmoset sera are being compared. Nitrogen compounds, nonprotein nitrogen compounds, non-nitrogenous organic compounds, vitamins, inorganic and ionic compounds, along with hematocrit, WBC, RBC and differential blood counts, are being determined to characterize a healthy animal and to identify problems before they become clinically evident. Improved analytic techniques are being developed and refined. Base-line data on nutrition are being accumulated from marmosets maintained in the indoor-outdoor environment. A computerized data bank is being established.